Optimal control of non-minimum phase integrating processes with time delay using disturbance observer-based control scheme

A systematical design method of optimal control for non-minimum phase integrating processes with time delay using disturbance observer-based (DOB) control scheme is presented. All stabilising controllers and the filter of DOBs for integrating plants are developed. Then the optimal set-point tracking controller and the optimal filter of DOB are systematically derived by minimising the H₂ norm performance specifications. The proposed design method has three main advantages. First, the design procedure is systematical and simple. Specified weight functions are chosen for step inputs and inputs similar to steps. The designed set-point tracking controller and the filter of DOB are given in analytical forms. Second, the designed set-point tracking controller and the filter of the DOB are optimal. They are derived from minimising the performance indexes of set-point tracking and input load disturbance rejection (ILDR). Finally, the set-point tracking performance specification and ILDR specification can be quantitatively achieved by conveniently tuning the adjustable parameters. Numerical simulations are given to illustrate the effectiveness of the proposed method.     

具有时滞的积分和不稳定对象的鲁棒控制

针对含时滞的积分和不稳定对象提出了一种新颖的两自由度控制结构,首先用一个比例控制器镇定给定值响应,然后基于鲁棒H₂最优性能指标设计给定值跟踪控制器.根据实际运行抗干扰要求,在对象输入和输出端之间设计负载扰动抑制闭环,利用扰动观测器抑制负载干扰信号,通过提出期望的闭环余灵敏度函数来确定扰动观测器,同时给出了扰动抑制闭环保证鲁棒稳定性的充要条件.最后通过仿真实例验证了该方法相对于近期其它方法的优越性.     

典型二阶积分对象的新型控制策略

针对工业控制中常见的一类具有时滞的二阶积分对象,根据内模控制原理,提出一种新型控制策略。在该结构中,由参考模型来实现系统期望的设定值跟随响应特性,利用内模控制鲁棒性强的特点来抑制参数变化和干扰对系统的影响,从而使系统获得良好的干扰抑制特性和鲁棒性。调节参考模型参数和内模控制器参数,可使系统同时具有良好的设定值跟随特性和干扰抑制特性。仿真结果表明了方法的优越性。     

一阶参数不确定滞后过程的鲁棒PID控制器设计

提出一种针对一阶参数不确定滞后过程的鲁棒PI／PID控制器优化设计方法。首先基于D-分割法技术,给出确定一阶参数不确定滞后过程的整个PI／PID控制器的可行鲁棒稳定域算法;在定义一个与控制器给定点跟踪性能、鲁棒性能和抗扰动性能相关的目标函数的基础上,给出PI／PID控制器设计的约束优化问题;最后应用一种启发式粒子群优化（PSO）算法对该约束问题进行求解。仿真结果表明,所提出的方法可得到更小的调节时间、更小的超调、较强鲁棒性和更好的抗扰动性能,表明了所提出的方法的有效性。     

Direct synthesis based tuning of the parallel control structure for integrating processes

A controller tuned for servo/regulatory application gives significant performance degradation when used for regulatory/servo purpose. The degradation in the overall performance can be minimised by a two degree-of-freedom control structure. The parallel control structure reported recently decouples set-point tracking from disturbance rejection. In the present work, the two controllers of parallel control structure are designed using direct synthesis approach to achieve robust closed-loop performance for a class of integrating processes. Simulation examples show that improved servo and regulatory performances are achieved by the proposed method as compared to the recently reported strategies when the controllers are tuned to have the same degree of robustness.     

Enhanced modified Smith predictor for second-order non-minimum phase unstable processes

In this paper, a modified Smith predictor design is proposed for enhanced control of non-minimum phase unstable second-order time-delay processes with/without zero. The proposed method involves the design of two controllers, i.e. set-point tracking controller and disturbance rejection controller. Set-point tracking controller is designed as a proportional-integral-derivative (PID) in series with a lag filter using direct synthesis method. The disturbance rejection controller is designed as a PID in series with a lead/lag filter based on direct synthesis method. Set-point weighting is considered for minimising the overshoots. The proposed method is applied by simulation on several second-order unstable processes. Robustness studies have been carried out using the small-gain theorem. The method gives good nominal and robust control performances. Significant improvement in the disturbance rejection is obtained with the proposed method when compared to the recently reported methods in the literature.     

直流位置伺服系统的二自由度分数阶控制

为提高直流位置伺服系统的控制性能,提出了一种2自由度（two degree-of-freedom,2DOF）分数阶控制方法．通过设计一种2DOF控制结构,实现了系统的跟随和抗扰特性的解耦控制;将内模控制（internal model control,IMC）与分数阶控制相结合,选用分数阶滤波器,推导出了跟随控制器和抗扰控制器设计方法;根据控制性能的要求,利用系统截止频率和最大灵敏度指标,实现了2DOF控制器参数的解析整定．仿真实验结果表明,2DOF分数阶控制方法具有良好的位置跟随特性和抗干扰能力．     

用直接综合法设计的微分先行鲁棒PID控制器

针对积分时滞系统应用直接综合方法设计了一种微分先行鲁棒PID控制器.这种方法基于比较积分时滞系统与后置超前滞后滤波器的微分先行PID控制器组成的闭环系统的特征方程和期望特征方程.期望特征方程由多个位于同一期望位置的极点组成.所设计的控制器的参数以实现期望鲁棒性的方式获得.通过选择不同的调优参数获取相应的Ms值,进而在参...     

Improved PI controller based on predictive functional control for liquid level regulation in a coke fractionation tower

Due to limitations of hardware, cost and so on, the application of proportional-integral-derivative (PID) control is more convenient than predictive control. However, predictive control usually has better performance than traditional PID control, thus it is important to combine the advantages of these two control algorithms. A novel PI controller optimized by predictive functional control (PFC) is proposed and tested on liquid level in the industrial coke fractionation tower in this paper. Since this kind of process always shows the integrating behavior, a P controller is first used for it to generate a self-balancing generalized process, then the PFC based PI control is designed for the generalized process. The resulting controller displays the performance of both PFC and PI control with easy implementation in practice. The performance of the proposed PI controller is compared with traditional PI controller in terms of regulatory/servo set-point tracking, disturbance rejection and measurement noise issues, from which results show that the proposed PI controller provides better performance than traditional PI controller.     

基于性能指标约束的一类输入死区非线性系统最优控制

针对一类考虑指定性能和带有输入死区约束的严格反馈非线性系统,本文提出了一种自适应模糊最优控制方法.采用模糊逻辑系统逼近系统的未知非线性函数及代价函数,利用backstepping方法及命令滤波技术,设计前馈控制器.针对仿射形式的误差系统,结合自适应动态规划技术,设计最优反馈控制器.采用指定性能控制方法,将系统跟踪误差约束在指定范围内.利用死区斜率信息解决具有死区输入的非线性系统的控制问题.基于Lyapunov稳定性理论,证明闭环系统内所有信号是一致最终有界的.最后仿真结果验证了本文方法的可行性和有效性.     

An alternative structure for next generation regulatory controllers: Part I: Basic theory for design, development and implementation

Even though employed widely in industrial practice, the popular PID controller has weaknesses that limit its achievable performance, and an intrinsic structure that makes tuning not only more complex than necessary, but also less transparent with respect to the key attributes of the overall controller performance, namely: robustness, set-point tracking, and disturbance rejection. In this paper, we propose an alternative control scheme that combines the simplicity of the PID controller with the versatility of model predictive control (MPC) while avoiding the tuning problems associated with both. The tuning parameters of the proposed control scheme are related directly to the controller performance attributes; they are normalized to lie between 0 and 1; and they arise naturally from the formulation in a manner that makes it possible to tune the controller directly for each performance attribute independently. The result is a controller that can be designed and implemented much more directly and transparently, and one that outperforms the classical PID controller both in set-point tracking and disturbance rejection while using precisely the same process reaction curve information required to tune PID controllers. The design, implementation and performance of the controller are demonstrated via simulation on a nonlinear polymerization process.     

H 2 input load disturbance rejection controller design for synchronised output regulation of time-delayed multi-agent systems with frequency domain method

An analytical H ₂ input load disturbance rejection (ILDR) controller design approach is presented for the synchronised output regulation (SOR) of homogeneous time-delayed multi-agent systems. First, a closed-loop multi-input multi-output framework with transfer functions is introduced, and an SOR condition is given. Second, the decomposition method is utilised to simplify the analysis of internal stability and H ₂ performance index of the whole system to a set of independent optimisation problems with respect to the eigenvalues of the topology matrix. Finally, for each decomposed subsystem, the H ₂ optimal ILDR controller can be computed from all the stabilising controllers. By comparison with the conventional given-structured controllers, the contributions of the new approach are that the design procedure is calculated analytically for multi-agent systems with input disturbances, and a simple quantitative tuning way is developed to trade-off the nominal performance and robustness. The simulation example shows the effective ILDR capability of the proposed control strategy.     

不稳定时滞对象的串级控制设计

针对常见的开环不稳定串级过程,提出一种新的解析设计方法.副回路中采用两自由度内模控制结构,减少因副回路设定值响应与扰动抑制响应耦合对主回路性能的影响.主回路采用加滤波器的单位反馈控制结构,基于闭环最优灵敏度函数解析推导出设定值响应控制器,保证系统的整体性能.针对副回路存在的乘性不确定性,分析了系统的鲁棒稳定性,最后通过...     

Simultaneous automatic tuning of cascade control systems from closed-loop step response data

This study presents a novel automatic tuning method for cascade control systems in which both primary and secondary controllers are tuned simultaneously using a single closed-loop step test. The proposed technique identifies the required process information with the help of B-spline series representation for the step responses. The two proportional–integral–derivative (PID) controllers are then tuned using an internal model control (IMC) approach. Considering the rationale of cascade control, the secondary controller is designed for faster disturbance attenuation. Without requiring an additional experiment, the primary controller is designed based on an identified process model that accurately accounts for inner loop dynamics. Finally, this study includes robustness considerations in the controller tuning process, and develops explicit guidelines for the selection of the IMC tuning parameters, completing the automatic tuning procedure for cascade control systems. The proposed method is robust to measurement noise because of the filtering property of the B-splines, and can provide superior control performance for both set-point tracking and disturbance rejection. Simulation examples demonstrate the effectiveness of the proposed automatic tuning method.     

Anti‐windup design of active disturbance rejection control for sampled systems with input delay

A novel anti‐windup design of active disturbance rejection control (ADRC) is proposed for industrial sampled systems with input delay and saturation. By using a generalized predictor to estimate the delay‐free system output, a modified extended state observer is designed to simultaneously estimate the system state and disturbance, which could become an anti‐windup compensator when the input saturation occurs. Accordingly, a feedback controller is analytically designed for disturbance rejection. By proposing the desired closed‐loop transfer function for the set‐point tracking, a prefilter is designed to tune the tracking performance while guaranteeing no steady‐state output tracking error. A sufficient condition for the closed‐loop system stability is established with proof for practical application subject to the input delay variation. Illustrative examples from the literature are used to demonstrate the effectiveness and merit of the proposed control design.     

基于优化性能的重复控制器设计

提出一种基于优化性能的重复控制器设计方法.首先,对重复控制器中时滞环节的时延进行修正,以补偿由于低通滤波器的引入所带来的相位滞后,进而提高系统在参考/干扰信号基频处的增益,增强系统对基频信号的跟踪/抑制能力;其次,在重复控制器中加入超前校正环节,不仅拓宽了低通滤波器的带宽,而且提高了系统的高频增益,使得系统在高次谐波处的性能得以大幅提升.重复控制器的参数通过求解2个优化问题得到.在保证系统稳定的前提下,提出的设计方法最大限度地提升了系统的性能.针对光盘驱动器控制系统的仿真结果证实了该设计方法的有效性.     

Some investigations on hybrid fuzzy IPD controllers for proportional and derivative kick suppression

Proportional and derivative kick i.e., a large change in control action of a proportional plus integral plus derivative (PID) controller due to a sudden change in reference set-point is generally undesired in process industry. Therefore, the structure of conventional parallel PID controller is modified to integral minus proportional derivative (I-PD) controller. In this paper, three hybrid fuzzy IPD controllers such as a fuzzy I-fuzzy PD (FI-FPD) controller and its hybrid combinations with its conventional counterpart such as fuzzy I-PD (FI-PD) and I-fuzzy PD (I-FPD) are presented in view of above industrial problem. These controllers are based upon the counterpart conventional I-PD controller and contains analytical formulae. Computer simulations are carried out to evaluate the performance of hybrid fuzzy controllers along with conventional I-PD and PID controllers for set-point tracking and disturbance rejection for an induction motor in closed loop using LabVIEW? environment. The gains of conventional and hybrid fuzzy controllers are tuned using genetic algorithm (GA) for minimum overshoot and settling time. It has been observed that hybrid fuzzy controllers along with the conventional I-PD controller significantly remove the kick from the control action in reference set-point tracking. However, in disturbance rejection, I-PD and FI-PD controllers fail to eliminate the kick from the control signal. In contrast, FI-FPD and I-FPD controllers considerably reduced spikes from the control action in disturbance rejection. Among the conventional and hybrid fuzzy IPD controllers, FI-FPD demonstrates much better set-point tracking and disturbance rejection response with spike free control action.     

Two degree-of-freedom design for a send-on-delta sampling PI control strategy

A complete event-based two-degree-of-freedom PI controller is presented. The architecture of the control system is based on two decoupled PI controllers, one for the set-point following and one for the load disturbance rejection task. The distinctive feature of the proposed approach is that the two controllers have the same parameters and the reference tracking performance is improved by suitably modifying the reference signal applied to the set-point following controller. Examples of the technique are given. In particular, the control strategy has been applied to a distributed solar collector field.     

一类工业过程运行反馈优化控制方法

为了克服流程工业运行优化中控制回路闭环系统的动态误差对运行优化性能的影响,本文针 对一类工业过程提出了使运行指标实际值与目标值偏差和控制回路输出与设定值跟踪误差的二次性能 指标极小化的运行优化反馈控制方法. 该方法由运行层设定值反馈控制和回路控制层设定值跟踪控制组成,其中设定值反馈控制采用基于LMI的 模型预测控制,回路控制采用衰减率可调的带有积分项的状态反馈调节律. 本文给出了保证运行优化反馈控制闭环系统渐近稳定的充分条件,并开展了浮选过程运行优化反馈控制仿 真实验,实验结果表明所提方法的有效性.     

双惯性伺服传动系统的抗扰动复合非线性控制

本文把复合非线性反馈(composite nonlinear feedback,CNF)控制技术推广到带有非定常扰动的输入饱和限幅的线性系统.其中,未知扰动被作为一个扩张状态量增广到被控对象的模型中,然后设计一个扩展状态观测器来对系统的状态量和扰动同时进行估计,通过在CNF控制的框架中引入一个扰动补偿机制,在降低由扰动引起的稳态误差的同时,保留了CNF原有的快速的瞬态性能.这种控制方案对定常或时变扰动、匹配或非匹配的扰动,都能统一处理.论文对该控制方案的闭环稳定性和定点跟踪性能进行了理论分析,并把它应用到一个双惯性伺服传动系统.数值仿真结果验证了该方案在定点跟踪控制中具有优越的瞬态性能和稳态精度,且对扰动/给定目标的幅值变化也有一定的性能鲁棒性.